1. Field of the Invention
Example embodiments relates to a grapple and a process for inserting, rearranging and/or removing control rods blades, fuel support castings and control rod guide tubes from fuel assemblies of a Boiling Water Reactor (BWR) nuclear core. The grapple may lift all three objects as a single unit during refueling operations and/or plant maintenance.
2. Related Art
The control rods in a boiling water reactor contain an absorbent material that when positioned in the reactor core can be used to slow the fission rate of the nuclear fuel. However, the absorbent material is subject to degradation after extended use. Therefore, it is periodically necessary to replace the control rods. Since different regions of the reactor core have different levels of irradiation fluence, in order to reduce expenses, it is common to periodically reposition the control rods within the core to maximize their useful life.
Conventionally, grapples have been used to grip the control rod blade and/or fuel support casting from the core. These grapples may remove the control rod blade and fuel support casting either individually, or in unison with each other. A separate grapple has conventionally been used to remove the control rod guide tube, adding time to the critical path during a refueling and maintenance outage.